Tape reel for use in magnetic tape cassette

ABSTRACT

A receiving surface ( 625 ) for use in the supersonic welding of the welding boss ( 620 ) of an M cassette tape reel ( 612   a ) is composed of the lower surface of a ring portion ( 626 ) which is formed so as to extend annularly along the base end of a hub central portion ( 621 ) formed in the bottom surface ( 616   a ) of a lower reel ( 616 ) and also which is projected downward (in FIG.  2 ) by a given amount from the bottom surface ( 616   a ). That is, the receiving surface ( 625 ) is situated slightly outside in the radial direction from directly below the welding boss ( 620 ).

FIELD OF THE INVENTION

The present invention relates to a tape reel for use in a magnetic tapecassette such as a digital video cassette (DVC). In particular, thepresent invention relates to a structure for improving a supersonicallywelding of a welding boss of a tape reel, a structure for improving thewinding shape of a magnetic tape to be wound around a tape reel, astructure for securing the dustproof property of a magnetic tapecassette when not in use as well as preventing the deformation of alower flange of a tape reel, a structure for preventing a magnetic tapefrom being damaged due to its contact with a tape reel, and a structurehaving a characteristic hub.

Also, the invention relates to a magnetic tape take-up device forwinding a magnetic tape around a tape reel and, in particular, to astructure for fixing the winding shape of a magnetic tape with the innersurface of an upper flange of a tape reel as a reference.

RELATED ART

Generally, in audio equipment and video equipment, there is often used amagnetic tape cassette structured such that a magnetic tape wound arounda pair of tape reels is runnably held within a cassette half to therebyexecute recording and reproduction.

Referring now to FIG. 20, conventionally, for example, as a magnetictape cassette which is used as a DVC (digital video cassette), there isknown a magnetic tape cassette 130 in which a pair of tape reels 131with a magnetic tape t wound therearound are rotatably supported withina lower cassette half 133 making a pair with an upper cassette half 132.

On both sides of an opening 134 formed on this side in FIG. 20 of thelower cassette half 133, there are disposed tape guides 135respectively. The two tape guides 135 respectively guide the magnetictape t which is fed out from one tape reel 131 and is taken up aroundthe other tape reel 131, and allow the magnetic tape t to pass through agiven position in the opening 134.

Also, on the rear side of the lower cassette half 133, there is disposeda reel lock member 139 having a tape reel securing arm 138. The reellock member 139 is energized by a compression coil spring 140 to bringthe tape reel securing arm 138 into engagement with two engaging teeth141 respectively formed on the outer peripheries of the two tape reels131, thereby preventing the unprepared rotation of the respective tapereels 131. This can prevent the wound magnetic tape t from loosening.

On the upper cassette half 132, there are mounted an outer lid 150 forcovering the opening 134 of the lower cassette half 133, an upper lid151 and an inner lid 152 in such a manner that they can be freely openedand closed.

On the two side plates 153 of the outer lid 150, there are projectinglyprovided lock pins 154, respectively. The two lock pins 154 arerespectively secured to their associated lid locks 155 which arerotatably disposed on the lower cassette half 133. By the way, referencecharacter 156 designates a lid spring to be mounted on the rotary shaftof the outer lid 150.

The tape reels 131 are respectively structured such that mutuallyopposing upper and lower flanges 142 and 143 are fixed with a givenposition relationship between them.

That is, in each tape reel 131, a pivot 147 projectingly provided on ahub 145 of the lower flange 143 is fitted into a pivot hole 146 formedin the central portion 144 of the upper flange 143. Also, a welding boss148, which is provided on and projected from the hub 145 of the lowerflange 143 at a position distant in the radial direction from the pivot147, is fitted into a welding boss hole 149 formed in the centralportion 144 of the upper flange 142 at a position corresponding to thewelding boss 148. In this state, in case where a welding horn (notshown) is contacted with the substantially central portion of theleading end face (in FIG. 20, the upper end face) of the welding boss148, the welding boss 148 can be welded supersonically. As a result ofthis, the mutually opposed upper and lower flanges 142 and 143 can befixed with a given position relationship between them.

Now, referring to FIGS. 20 and 21, on the bottom surface 143 a of thelower flange 143 that is situated on the opposite side of the hub 145,there is disposed a reference ring 157 which provides a reference forworking using a metal mold. The reference ring 157 is present at aposition which is more distant in the radial direction than the weldingboss 148. The surface 157 a of the reference ring 157 is used as areceiving surface for receiving the welding boss 148 when it is weldedsupersonically, because the surface 157 a makes it possible tofacilitate the grasping of the dimensional relationship. That is, incase where the surface 157 a of the reference ring 157 is contacted witha welding receiving base (not shown) when the welding boss 148 is weldedsupersonically, the surface 157 a allows the welding receiving base toreceive pressures applied from the welding horns and vibrations causedby the supersonic oscillation.

In the above-mentioned conventional magnetic tape cassette 130, thesurface 157 a of the reference ring 157 is used as the receiving surfacewhen the welding boss 148 is supersonically welded. Due to this, theoscillation energy of the supersonic waves from the welding horns is inpart lost due to the resonance of the components of the tape reel 131existing from the welding boss 148 to the reference ring 157, resultingin the low transmission efficiency of the oscillation energy of thesupersonic waves from the welding horn to the welding boss 148. In casewhere the transmission efficiency of the oscillation energy of thesupersonic waves is low, it takes time to weld the welding boss 148,which makes it necessary to extend the oscillation time of thesupersonic waves, resulting in the poor mass-production aptitude and inthe poor welding stability. Further, in case where the welding stabilityis poor, there is a fear that the mutually opposing attitudes of theupper and lower flanges 142 and 143 can be out of balance, giving riseto the vibratory motion of the surfaces of the tape reel 131 when it isrotated.

It is a first object of the invention to provide a tape reel for use ina magnetic tape cassette which can enhance the transmission efficiencyof the oscillation energy of the supersonic waves to the welding boss tothereby be able to shorten the time necessary for supersonic welding ofthe welding boss as well as to enhance the welding stability.

Next, referring to FIG. 22, the inner surface (lower surface) of theupper flange 142 is formed as a sloping surface 142 b which graduallyslopes upward from the base end portion (in FIG. 22, the upper endportion a) of the side wall 145 b of the hub 145 toward theradial-direction outer side (in FIG. 22, the right side) of the upperflange 142. Also, the inner surface (upper surface) of the lower flange143 is formed as a sloping surface 143 b which gradually slopes downwardfrom the base end portion (in FIG. 22, the lower end portion b) of theside wall 145 b of the hub 145 toward the radial-direction outer side(in FIG. 22, the right side) of the lower flange 143.

However, in case where such slopes are formed on the whole areas of thelower surface of the upper flange and the lower surface of the lowerflange, it is true that, when the magnetic tape is wound, it can bewound easily; but, there is also a fear that the magnetic tape can bevibrated in the vertical direction.

In case where a given period of time passes after the winding operationof them magnetic tape is started, the rotation speed of the reel drivemeans and the tape tension become constant, so that the magnetic taperuns stably and thus there is no fear that it can be vibrated in thevertical direction. However, at the beginning of the winding operationof the magnetic tape, the rotation speed of the reel drive meansincreases gradually and the tape tension also increases, so that themagnetic tape is not be able to run stably.

In this case, since the magnetic tape is vibrated in the verticaldirection, the side edges of the wound magnetic tape cannot besuperimposed on each other in a well-arranged manner, so that the woundsurface of the magnetic tape to be formed by the side edges of themagnetic tape can be out of order and thus it cannot provide a flatsurface; that is, there arises a problem that the magnetic tape cannothave a fine winding shape.

Accordingly, it is a second object of the invention to solve the aboveproblem: that is, it is a second object of the invention to provide amagnetic tape reel which allows a magnetic tape to provide a finewinding shape after it is wound.

Next, referring to FIG. 23, on the edge portions of reel holes 133 aformed in the inner surface (in FIG. 23, the upper surface) of the lowercassette half 133, there are provided annular-shaped projecting portions133 b, respectively. These annular-shaped projecting portions 133 b,when the magnetic tape cassette 130 is not in use (that is, in the statethereof shown in FIG. 23), are respectively contacted with the outersurfaces of the lower flanges 141 of the respective tape reels 131. Dueto this, the annular-shaped projecting portions 133 b are respectivelyable not only to prevent entry of dust into the interior of the magnetictape cassette 130 as much as possible but also to support the weights ofthe respective tape reels 131 and the weight of the magnetic tape twound around the respective tape reels 131.

In the above-mentioned magnetic tape cassette 130, in case where therespective tape reels 131 increase in size (outside diameter), when themagnetic tape cassette 130 is not in use, the lower flanges 141 of therespective tape reels 131 are not be able to support the weight of themagnetic tape t, thereby raising a problem that the portions of thelower flanges 141, which are present outside the contact portions of thelower flanges 141 with their associated annular-shaped projectingportions 53 b, can be flexed.

In this case, in case where the thicknesses of the lower flanges 141 ofthe respective tape reels 131 are increased, the above problem can besolved. However, in case where the thicknesses of the lower flanges 141increase, there arises another problem that there cannot be secured aclearance between the lower flanges 141 and lower cassette half 133 whenthe magnetic tape cassette 130 is not in use. In case where suchclearance cannot be secured, for example, there arises an inconveniencethat, due to the vibrations of the magnetic tape cassette half 130 whenit is delivered, the lower flanges 141 and lower cassette half 133 areslidingly contacted with each other.

Accordingly, it is a third object of the invention to provide a magnetictape cassette which can secure a high dust-proof condition in theinterior thereof when it is not in use, can positively prevent the lowerflanges of the tape reels against deformation, and can secure asufficient clearance between the lower flanges and a lower cassettehalf.

Next, referring to FIG. 24, conventionally, as a magnetic tape cassettefor a beta cam, for example, there is known a magnetic tape cassette 230in which a pair of tape reels 231 with a magnetic tape t woundtherearound are rotatably supported within a lower cassette half 233which makes a pair with an upper cassette half 232.

On the two sides of an opening 234 formed on this side in FIG. 24 of thelower cassette half 233, there are disposed tape guides 235respectively. The tape guides 235 respectively guide the magnetic tapet, which is fed out from one tape reel 231 and is then taken up aroundthe other tape reel 231, and allows the magnetic tape t to pass througha given position in the opening 234. On the other hand, on the uppercassette half 232, there is openably and closably mounted a lid 250which covers the opening 234 of the lower cassette half 233.

The tape reels 231 are respectively structured such that, with a givenclearance formed between the mutually opposed upper and lower flanges242 and 243, the central portion 244 of the upper flange 242 and the hub245 of the lower flange 243.

That is, in each of the tape reels 231, a pivot 247 provided on the hub245 of the lower flange 243 is fitted into a pivot hole 246 formed inthe central portion 244 of the upper flange 242. Also, a plurality ofwelding bosses 248, which are provided on and projected from the hub 245of the lower flange 243 at positions spaced from the pivot 247 in theradial direction of the hub 245, are respectively fitted into aplurality of welding boss holes 249 formed in the central portion 244 ofthe upper flange 242 at positions corresponding to the welding bosses248.

In this state, in case where welding horns (not shown) are respectivelycontacted with the substantially central portions of the leading endfaces of the respective welding bosses 248, the welding bosses 248 canbe welded supersonically. As a result of this, the mutually opposedupper and lower flanges 242 and 243 can be fixed with a given clearancebetween them.

Referring here to FIG. 25, when the lower flange 243 is molded using ametal mold, in the surface 243 a (in FIG. 25, the upper surface) of thelower flange 243 that is disposed opposed to the upper flange 242, thereare formed a plurality of air discharging recessed portions 251 (in FIG.24, not shown) which are spaced at given intervals in the peripheraldirection of the opposed surface 243 a. The respective air dischargingrecessed portions 251 discharge the air, which enters the interior ofthe tape reel together with the magnetic tape t when the magnetic tape tis taken up around the tape reel, externally of the tape reel to therebyprevent the magnetic tape t from being wound in disorder.

In the above-mentioned conventional magnetic tape cassette 230 for abeta cam, substantially over the entire periphery of the edge portions252 of the air discharging recessed portions 251 of the lower flanges243, there are generated edges 253 when the magnetic tape cassette 230is molded using a metal mold. This raises a problem that, when themagnetic tape t is taken up around the tape reel, the edges 253 can becontacted with the magnetic tape t, thereby causing the magnetic tape tto be damaged.

This problem, recently, with the enhanced density of the magnetic taperecording, has a seriously ill effect on the recording accuracy and,especially, in a magnetic tape cassette for business such as a beta cam,this problem is serious.

Accordingly, it is a fourth object of the invention to provide amagnetic tape cassette which can prevent a magnetic tape against damagedue to its contact with a tape reel to thereby be able to cope with theenhanced density of the magnetic tape recording.

Also, in the case of a tape reel of the above-mentioned type, since theheight of the hub thereof is slightly larger than the width of amagnetic tape, while the magnetic tape is being wound around the tapereel, the magnetic tape can be moved up and down when it is moved in theaxial direction of the hub, with the result that the magnetic tape woundaround the hub of the tape reel can be projected in part in the axialdirection of the hub. In order to prevent this, in JP-A-58-187083U,there is disclosed a tape reel structured such that the peripheralsurface of the hub thereof is inclined with respect to the axialdirection of the hub. Here, FIG. 26(a) is a section view of the tapereel set forth in the above-cited publication, and FIG. 26(b) is aschematic side view of the hub of the present tape reel.

Specifically, in the conventional tape reel shown in FIG. 26, on theupper and lower surfaces of a hub 320, there are disposed upper andlower flanges 322 and 324; the hub 320 and lower flange 324 are formedof resin as an integral body; and, the central portion of the resin-madeupper flange 322, which is produced separately from the hub 320, issupersonically welded to the upper end of the hub 320. Although theouter peripheral surface 320 a of the hub 320 is circular, the centerline A of the circular-shaped outer peripheral surface 320 a is inclinedby a given angle θ with respect to the axial direction B of the hub 320.Also, the mutually opposed inner surfaces 322 a and 324 a of the upperand lower flanges 322 and 324 are respectively formed as slopingsurfaces which spread out as they go outwardly in the radial directionthereof. The peripheral surfaces of the hub 320 are inclined over theentire areas thereof; and, the peripheral surfaces of the hub 320, whichare disposed 180° opposed to each other when the hub 320 is viewed fromthe top plan thereof, are inclined in different directions in the axialdirection of the hub 320.

According to the above tape reel, since a magnetic tape 326 to be woundaround the hub 320 is contacted with either o f the upper flange 322 orlower flange 324 at each angle of 180° when the hub 320 is viewed fromthe top plan thereof and is thereby restricted in the vertical movementthereof, the magnetic tape 326 can be wound around the hub 320 withoutbeing projected in part in the axial direction B of the hub 320.

By the way, generally, the pulling direction of a molding, that is, amolded hub from a metal mold is equal to the axial direction of the hub.However, in the case of the hub 320 shown in FIG. 26 in which theperipheral surfaces of the hub 320 disposed 180° opposed to each otherwhen the hub 320 is viewed from the top plan thereof slope in differentdirections in the axial direction of the hub 320, after it is injectionmolded, it cannot be pulled out from the metal mold along the axialdirection B thereof as it is. For this reason, to manufacture the hub320, there is necessary a metal mold using a slide core, which not onlycomplicates the structure of a metal mold but also makes it difficult tomanufacture the hub 320.

Accordingly, it is a fifth object of the invention to solve the aboveproblem; in particular, to provide a magnetic reel which is easy tomanufacture and around which a magnetic tape can be wound with a goodwinding shape, and a method for manufacturing such tape reel.

Next, as a magnetic tape take-up apparatus, conventionally, in JapanesePatent Unexamined Publication No. Hei.1-217782, there is disclosed amagnetic tape take-up apparatus 440 structured such that, as shown inFIG. 27, a magnetic tape 444 being wound around a tape reel 441 isenergized in the direction of a lower flange 442 not in contact with thelower flange 442 by a permanent magnet 443 disposed opposed to the lowerflange 442 of the tape reel 441 to thereby arrange the winding shape ofthe magnetic tape 444 with the inner surface of the lower flange 442 asa reference surface.

The tape reel 441 is mounted on the rotary shaft 446 of a drivemechanism 445 and, in case where the tape reel 441 is driven or rotatedby the drive mechanism 445, it takes up the magnetic tape 444 from atape supply source onto a tape winding surface 447. The permanent magnet443 is formed in a doughnut shape; and, with the rotary shaft 446 of thedrive mechanism 445 loosely fitted into a through hole 448, thepermanent magnet 443 is supported through a support portion 449 on atake-up apparatus main body 450.

In the above-mentioned conventional magnetic tape take-up apparatus 440,the permanent magnet 443 is disposed opposed to the lower flange 442 ofthe tape reel 441 and is used to arrange the winding shape of themagnetic tape 444 with the inner surface of the lower flange 442 as areference surface.

Therefore, there arises a problem that, when a magnetic tape cassette isset on a recording and reproducing apparatus and the magnetic tape 444is then made to run, the running passage of the magnetic tape 444,through which it is made to run for the first time by the recording andreproducing apparatus, is shifted from the running passages thereofthrough which it is made to run for the second time and following times.

That is, for example, in such a recording and reproducing apparatus 460as shown in FIG. 28, in the first tape running, a magnetic tape 462,which is wound around a tape reel 461 by the conventional magnetic tapetake-up apparatus 440, runs through a passage which is shifted to thelower side in FIG. 28 as shown by a two-dot chained line shown in FIG.28. The reason for this is as follows: that is, since the lower flangeof the tape reel 461 has a taper surface sloping downward toward theradial direction of the tape reel 461, the magnetic tape 462 woundaround the tape reel 461 is caused to lower downward gradually towardits outer periphery side. In the second and following tape runnings inwhich the magnetic tape 462 rewound around the tape reel 461 by themagnetic tape take-up apparatus 440 is made to run again, the magnetictape 462 runs through its normal running passage which is shown by asolid line in FIG. 28. Thus, the running passage of the magnetic tape isshifted between the first tape running and the second and following taperunnings by the recording and reproducing apparatus 460.

Now, description will be given below in detail of the cause of theshifted running passage of the magnetic tape 462.

Firstly, referring to the running passage of the magnetic tape 462 inthe magnetic tape take-up apparatus 440, the magnetic tape 462, which isplayed out from the tape reel 461 of the magnetic tape cassette 463, isguided by tape guides TG0, TG1, TG2 and TG3. This defines the mutuallyrelative positions of the magnetic tape 462 and a recording andreproducing head 464 (cylinder).

In other words, the magnetic tape 462 drawn out from the tape reel 461is once raised up to its upper limit position by the tape guide TG1through the tape guide TG0 and the position of the magnetic tape 462 atthe upper limit position is controlled by the tape guide TG1; and, afterthen, the position of the magnetic tape 462 is controlled to itsoriginal position between the tape guides TG2 and TG3, and the magnetictape 462 is then contacted with the recording and reproducing head 464at a given relative position.

However, in case where the magnetic tape 462 is wound around the tapereel 461 by the conventional magnetic tape take-up apparatus 440, sincethe lower flange has a taper surface, the play-out position of themagnetic tape 462 from the tape reel 461 is a low position (a positionwhich near to the lower flange 466) shown by a two-dot chained line inFIG. 28.

Due to this, the magnetic tape 462 drawn out from the tape reel 461, asshown by the two-dot chained line in FIG. 28, is not be able to reachthe upper limit position to which it ought to be guided by the tapeguide TG1; and, therefore, without being controlled in position at theupper limit position by the tape guide TG1, the magnetic tape 462 iscontrolled in position by the tape guides TG2 and TG3. As a result ofthis, the running passage of the magnetic tape 462 between the tapeguides TG2 and TG3 is shifted from its normal or original runningpassage. This phenomenon occurs more outstandingly as the magnetic tape462 wound is present on the outer periphery side.

In case where, as described above, the running passage of the magnetictape 462 is shifted between the first tape running and the second andfollowing tape runnings by the recording and reproducing apparatus 460,the relative positions of the magnetic tape 462 and recording andreproducing head 464 in the first tape running is different from therelative positions of the magnetic tape 462 and recording andreproducing head 464 in the second and following tape runnings. As aresult of this, there arises a problem that, in the recording andreproducing states of the magnetic tape 462, there occurs a seriousfault, such as poor interchangeability which cannot be repaired.

Accordingly, it is a sixth object of the invention to provide a magnetictape take-up apparatus which can arrange the winding shape of a magnetictape with the upper flange of a tape reel as a reference to thereby beable to stabilize the running of the magnetic tape in a recording andreproducing apparatus.

DISCLOSURE OF THE INVENTION

In attaining the above-mentioned first object, according to a firstinvention, there is provided a tape reel for use in a magnetic tapecassette, comprising: an upper flange; and, a lower flange disposedopposed to the upper flange and including a hub on the surface thereofopposed to the central portion of the upper flange, wherein a pivotprovided on and projected from the hub is fitted into a pivot holeformed in the central portion of the upper flange, a welding bossprojectingly disposed at a position of the hub distant from the pivot inthe radial direction of the hub is fitted into a welding boss holeformed in the central portion of the upper flange, and, in this state,the welding boss is welded supersonically, whereby the upper and lowerflanges are fixed with a given position relationship between them,characterized in that, on the opposite surface of the lower flange tothe hub, there are disposed not only a reference ring which is used as areference for working the tape reel using a metal mold but also,radially inside the reference ring, a receiving surface for use in thesupersonic welding of the welding boss.

In the tape reel for use in a magnetic tape cassette according to thefirst invention, the pivot projectingly provided on the hub formedintegral with the lower flange is fitted into the pivot hole formed inthe central portion of the upper flange. Also, the welding bossprojectingly disposed at a position of the hub distant from the pivot inthe radial direction of the hub is fitted into the welding boss holeformed in the central portion of the upper flange. In this state, thewelding boss is welded supersonically. Due to this, the upper and lowerflanges are fixed with a given position relationship between them.

On the opposite surface of the lower flange to the hub, there isdisposed the reference ring which is used as a reference for working thetape reel using a metal mold and, in the portion of the opposite surfaceof the lower flange to the hub that is situated internally of thereference ring in the radial direction of the tape reel, there is formedthe receiving surface for use in the supersonic welding of the weldingboss.

In case where the receiving surface, in the supersonic welding of thewelding boss, is contacted, for example, with a welding receiving base,the welding boss allows the welding receiving base to receive not onlypressures applied from welding horns but also vibrations caused by theoscillation of the supersonic waves. In this case, since the receivingsurface is situated in the portion of the opposite surface of the lowerflange to the hub that is situated internally of the reference ring inthe radial direction of the tape reel, the oscillation energy of thesupersonic waves from the welding horns can be prevented from being lostby the resonance of the components disposed from the welding boss to thereference ring.

Also, in attaining the above second object, according to a secondinvention, there is provided a magnetic tape reel, comprising: a hub forwinding a magnetic tape therearound; and, upper and lower flangesrespectively positioned on the upper and lower ends of the hub, each ofthe inner surfaces of the upper and lower flanges being formed so as toslope outwardly in the radial direction of the magnetic tape reel,wherein, on the adjacent portions of the upper and lower flanges to thehub, there are respectively formed flat surfaces lying at right anglesto the side surface of the hub and having a given width in the radialdirection of the magnetic tape reel.

The radial-direction width of each of the flat surfaces may bepreferably larger than the tape winding thickness obtained before, inthe tape take-up operation, the motor speed or the tape tensile forcebecomes constant from the beginning of the tape take-up operation, thatis, before the tape take-up ability becomes constant. Specifically, forexample, in the case of the above-mentioned DVC, for all sizes of S, M,L, the radial-direction width of the flat surface may be larger than thethickness of a clamp for fixing a tape to the hub, in more specifically,the width may be preferably set in the range of 0.5-5.0 mm.

Also, the clearance between the upper and lower flat surfaces may be setslightly larger than the width of the magnetic tape and may be set asnarrowly as possible so long as it does not provide any obstacle to therunning of the magnetic tape.

According to the second invention, the portions of the flanges existingin the periphery of the hub do not slope but the flanges are parallel toeach other and, in the beginning of the winding operation of themagnetic tape, there is no room for the magnetic tape to move up anddown; and, therefore, the winding surface of the magnetic tapeconsisting of the side edges of the magnetic tape is arranged uniformly,thereby allowing the magnetic tape wound to have a good winding shape.

Also, in attaining the above third object, according to a thirdinvention, there is provided a magnetic tape cassette, comprising: atape reel including upper and lower flanges, the upper and lower flangesbeing disposed opposed to each other and fixed with a given positionrelationship between them; an upper cassette half; and, a lower cassettehalf disposed opposed to the upper cassette half, the lower cassettehalf being capable of storing the tape reel in an internal space formedbetween the upper cassette half and itself, the lower cassette halfincluding a reel hole for insertion and removal of tape reel drivemeans, wherein the lower flange of the tape reel includes alarge-thickness stepped portion formed so as to be continuous with anoutside annular-shaped rib, while the portion of the large-thicknessstepped portion opposed to the edge portion of the reel hole of thelower cassette half has a thickness set at a given value or more.

Also, in attaining the above third object, according to a fourthinvention, there is provided a magnetic tape cassette, comprising: atape reel including upper and lower flanges, the upper and lower flangesbeing disposed opposed to each other and fixed with a given positionrelationship between them; an upper cassette half; and; a lower cassettehalf disposed opposed to the upper cassette half, the lower cassettehalf being capable of storing the tape reel in an internal space formedbetween the upper cassette half and itself, the lower cassette halfincluding a reel hole for insertion and removal of tape reel drivemeans, wherein, on the edge portion of the reel hole formed in the innersurface of the lower cassette half, there is disposed an annular-shapedprojecting portion and, on the radial-direction outside of theannular-shaped projecting portion, there is formed an annular-shapedrecessed portion, and, also wherein, in a position which is present inthe outer surface of the lower flange of the tape reel and is opposed tothe annular-shaped recessed portion, there is disposed an annular-shapedprojection to be loosely fitted into the annular-shaped recessedportion.

In the magnetic tape cassette according to the third invention, when thepresent magnetic tape cassette is not in use, the large-thicknessstepped portion formed so as to be continuous with an outsideannular-shaped rib, with the portion thereof opposed to the edge portionof the reel hole of the lower cassette half having a thickness set at agiven value or more, is contacted with the edge portion of the reel holeof the lower cassette half.

In this state, entry of dust into the interior of the magnetic tapecassette can be prevented and thus a highly dust-proof effect can besecured.

Also, tape reels and a magnetic tape wound around the tape reels aresupported on the lower cassette half through the large-thickness steppedportions of the lower flanges of the tape reels with the portionsthereof having a thickness set at a given value or more. Not only due tosuch support of the tape reels through the large-thickness steppedportions of the lower flanges formed continuous with the outsideannular-shaped ribs and having a thickness set at a given value or morebut also due to the enhanced rigidity of the lower flanges of the tapereels by the portions of the lower flanges having a thickness set at agiven value or more, even in a tape reel having a large diameter,deformation of the lower flange of the tape reel due to the weight ofthe magnetic tape can be prevented positively. Thanks to this, when themagnetic tape cassette is not in use, there can be secured a sufficientclearance between the lower flanges of the tape reels and lower cassettehalf.

In the magnetic tape cassette according to the fourth invention, whenthe present magnetic tape cassette is not in use, the annular-shapedprojecting portion of the lower half cassette is contacted with theouter surfaces of the lower flanges of the tape reels, and theannular-shaped projections of the lower flanges are loosely fitted intothe annular-shaped recessed portion of the lower cassette half and arethereby contacted with the lower cassette half.

In this state, entry of dust into the interior of the magnetic tapecassette can be prevented and thus a highly dust-proof effect can besecured.

Also, tape reels and a magnetic tape wound around the tape reels aresupported on the lower cassette half through the annular-shapedprojecting portion of the lower cassette half and the annular-shapedprojections of the lower flanges. Due to support of the tape reelsthrough the annular-shaped projecting portion of the lower cassette halfand the annular-shaped projections of the lower flanges, even in a tapereel having a large diameter, deformation of the lower flange of thetape reel due to the weight of the magnetic tape can be preventedpositively. Thanks to this, when the magnetic tape cassette is not inuse, there can be secured a sufficient clearance between the lowerflanges of the tape reels and lower cassette half.

And, in attaining the above fourth object, according to a fifthinvention, there is provided a magnetic tape cassette including a tapereel, the tape reel comprising: an upper flange; and, a lower flangedisposed opposed to the upper flange and fixed with a given positionrelationship with respect to the upper flange, the lower flangeincluding a hub providing a winding surface for winding a magnetic tapetherearound, wherein, in the surface of the upper flange that is opposedto the lower flange, or, in the surface of the lower flange that isopposed to the upper flange, there is formed an air discharging recessedportion or an air discharging penetration hole for discharging out theair entering together with a magnetic tape when the magnetic tape iswound around the reel, and, also wherein the edge portions of two sidesof the air discharging recessed portion or the air dischargingpenetration hole in at least radial direction of the flanges are formedinto a curve-shape respectively.

In the magnetic tape cassette according to the fifth invention, when themagnetic tape is taken up around the tape reel, the air dischargingrecessed portion or air discharging penetration hole functions as a flowpassage for discharging the accompanying air, thereby being able toprevent the magnetic tape from being wound in disorder. In this case,even when the magnetic tape is contacted with the edge portion of theair discharging recessed portion of the tape reel, the required curvedshape applied to the edge portion can prevent the magnetic tape againstdamage.

Also, in attaining the above fifth object, according to a sixthinvention, there is provided a magnetic tape reel, wherein the outersurface of a clamp member for holding a leader tape between itself and arecessed portion formed in a hub for winding a magnetic tape therearoundand the peripheral surface of the hub that, when viewed from the topplan surface of the hub, is disposed 180° opposed to the recessedportion are respectively taper surfaces which slope in mutuallydifferent directions in the axial direction of the magnetic tape reel.

Further, in attaining the above fifth object, according to a seventhinvention, there is provided a method for manufacturing a magnetic tapereel having a structure that, in a hub for winding a magnetic tapetherearound, there is formed a recessed portion for holding a leadertape using a clamp member, and the peripheral surface of the hub that,when viewed from the top plan surface of the hub, is disposed 180°opposed to the recessed portion is a taper surface sloping toward theaxial direction of the hub, the method comprising the steps of:injection molding the magnetic tape reel; and, pulling out the injectionmolded magnetic tape reel along the axial direction thereof.

According to the sixth and seventh inventions, the hub includes thesloping peripheral surface only on one side thereof and the recessedportion of the hub, which is formed on the opposite side of the slopingperipheral surface and into which the clamp member can be fitted, doesnot have any gradient. Therefore, after the magnetic tape reel ismolded, the hub, as it is, can be pulled out along the axial directionof the magnetic tape reel. This does not require a complicated metalmold using a slide core and thus the hub can be manufactured easilyusing a metal mold having a simple structure.

Also, in the case of the clamp member, there is formed a sloping surfaceon the peripheral surface thereof but, after it is injection molded, itcan be pulled out along the axial direction thereof as it is. Therefore,also when manufacturing the clamp member, there is not required acomplicated metal mold using a slide core and thus the clamp member canbe manufactured easily using a metal mold having a simple structure.

Further, in attaining the above sixth object, according to an eighthinvention, there is provided a magnetic tape take-up apparatus,comprising: drive means for rotating a tape reel to thereby wind amagnetic tape around the tape reel at a winding speed of 2-2.5 m/s andwith a winding tension of 60-70 g; and, magnetic field generating meansincluding a magnet formed of neodymium and having a magnetic fluxdensity of 12800-13300 G, and disposed opposed to the upper flange ofthe tape reel with a clearance of 12-17 mm between them for applying amagnetic field to the magnetic tape from the upper flange side of thetape reel.

The area of the portion of the magnetic field generating means opposedto the upper flange of the tape reel may be preferably 1.3 times or morethe area of the side surface side of the magnetic tape to be woundaround the tape reel.

In the magnetic tape take-up apparatus according to the eighthinvention, the drive means rotates the tape reel to thereby wind amagnetic tape from a tape supply source around the tape reel at awinding speed of 2-2.5 m/s and with a winding tension of 60-70 g. Also,the magnetic field generating means including a magnet formed ofneodymium and having a magnetic flux density of 12800-13300 G applies amagnetic field to the magnetic tape from a position where it is opposedto the upper flange of the tape reel with a clearance of 12-17 mmbetween them. Due to this, the magnetic field given by the magneticfield generating means can be applied uniformly to the magnetic tapefrom the upper flange side of the tape reel.

In the magnetic tape take-up apparatus according to the eighthinvention, the area of the portion of the magnetic field generatingmeans opposed to the upper flange of the tape reel, preferably, may beset 1.3 times or more the area of the side surface side of the magnetictape to be wound around the tape reel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a lower cassette half of a magnetic tapecassette incorporating therein a tape reel according to an embodiment ofthe first invention;

FIG. 2 is a section view of a tape reel for an M cassette;

FIG. 3 is a bottom plan view of the M cassette tape reel shown in FIG.2, taken along the arrow mark A in FIG. 2;

FIG. 4 is a section view of a tape reel for an L cassette;

FIG. 5 is a bottom plan view of the L cassette tape reel shown in FIG.4, taken along the arrow mark B in FIG. 4;

FIG. 6 is a half section view of the main portions of a magnetic tapereel according to an embodiment of the second invention;

FIG. 7 is a plan view of a lower cassette half of a magnetic tapecassette according to a first embodiment of the third invention;

FIG. 8 is a section view of the main portions of the magnetic tapecassette shown in FIG. 7;

FIG. 9 is a section view of the main portions of a magnetic tapecassette according to a second embodiment of the third invention;

FIG. 10 is a plan view of a lower flange of a tape reel of a magnetictape cassette according to an embodiment of the fourth invention;

FIG. 11 is a section view of the lower flange shown in FIG. 10, takenalong the arrow line A—A in FIG. 10;

FIG. 12 is an enlarged section view of the B portion of the lower flangeshown in FIG. 11;

FIG. 13 is an exploded plan view of a hub and a clamp member included ina magnetic tape reel according to an embodiment of the fifth invention;

FIG. 14(a) is a plan view of the hub and clamp member included in themagnetic tape reel according to the embodiment of the fifth invention,showing their combined state, and FIG. 14(b) is a side view thereof;

FIG. 15(a) is a plan view of a hub and a clamp member included in amagnetic tape reel according to another embodiment of the fifthinvention, showing their combined state, and FIG. 15(b) is a side viewthereof;

FIG. 16 is a schematic plan view of a magnetic tape take-up apparatusaccording to an embodiment of the eighth invention;

FIG. 17 is a graphical representation of the relationship between awinding speed and a pivot portion temperature;

FIG. 18 is a graphical representation of the relationship between awinding speed and a poor winding shape occurrence rate;

FIG. 19 is a graphical representation of the relationship between awinding tension and a poor winding shape occurrence rate;

FIG. 20 is an exploded perspective view of a conventional magnetic tapecassette (DVC);

FIG. 21 is a bottom plan view of a conventional L cassette tape reel;

FIG. 22 is a half section view of a conventional magnetic tape reel;

FIG. 23 is a section view of the main portions of a conventionalmagnetic tape reel;

FIG. 24 is an exploded perspective view of a conventional magnetic tapecassette (beta cam);

FIG. 25 is an enlarged section view of the main portions of a lowerflange of a tape reel used in the magnetic tape cassette shown in FIG.24;

FIG. 26(a) is a section view of a conventional magnetic tape reel, andFIG. 26(b) is a schematic side view of a hub;

FIG. 27 is a schematic section view of the main portions of aconventional magnetic tape take-up apparatus; and,

FIG. 28 is a schematic side view of the main portions of a recording andreproducing apparatus for recording and reproducing a magnetic tapecassette.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, description will be given below of the preferred embodiments of theinvention with reference to the accompanying drawings.

FIG. 1 is a plan view of a lower cassette half of a magnetic tapecassette to which a tape reel according to an embodiment of the firstinvention is applied. Also, FIG. 2 is a section view of a tape reel foran M cassette and FIG. 3 is a bottom plan view of the M cassette tapereel shown in FIG. 2, taken along the arrow mark A in FIG. 2. Further,FIG. 4 is a section view of a tape reel for an L cassette and FIG. 5 isa bottom plan view of the L cassette tape reel shown in FIG. 4, takenalong the arrow mark B in FIG. 4.

In FIG. 1, a magnetic tape cassette 610 of an M size or an L size isstructured such that a pair of tape reels 612 a, 612 b (in FIG. 1, atape reel disposed on the right side is not shown) with a magnetic tapet (see FIG. 20) wound therearound are rotatably supported on a lowercassette half 611 making a pair with an upper cassette half (not shown).The lower cassette half 611 is integrally molded of synthetic resin suchas ABS resin.

Referring to FIGS. 1 to 5, the tape reel 612 a of the magnetic tapecassette 610 of an M size (which is hereinafter referred to as Mcassette tape reel 612 a), or the tape reel 612 b of the magnetic tapecassette 610 of an L size (which is hereinafter referred to as Lcassette tape reel 612 b) includes an upper flange 614, and a lowerflange 616 disposed opposed to the upper flange 614 and including a hub615 provided on the surface thereof that is opposed to the centralportion 613 of the upper flange 614.

The upper and lower flanges 614 and 616 are fixed with a given positionrelationship between them. The upper flange 614 is integrally molded of,for example, transparent synthetic resin, whereas the lower flange 616is integrally molded of, for example, opaque synthetic resin.

In the upper flange 614, there are formed a pivot hole 617 and a weldingboss hole 618. The pivot hole 617 is formed so as to penetratesubstantially through the center of the central portion 613 of the upperflange 614. The welding boss hole 618 is formed so as to penetratethrough the position of the central portion 613 of the upper flange 614that corresponds to a welding boss 620 (which will be discussed later),while the number of welding boss holes 618 is set equal to the number ofwelding bosses 620.

Referring here to FIGS. 1, 2 and 4, in the case of the lower flange 616,there are projectingly provided a pivot 619 and a welding boss 620 onthe upper surface of the hub 615. That is, the hub 615 is structuredsuch that: on the periphery thereof that is distant in the radialdirection from a hub central portion 621 thereof, there is formed a sidewall 622 serving as a winding surface for a magnetic tape t; and, thehub central portion 621 and side wall 622 are connected together by aplurality of ribs 623 extending along the radial direction of the hub615:

The pivot 619 is provided on and projected from the center of the uppersurface of the hub central portion 621. Also, in the case of the weldingboss 620, two or more units (in FIG. 1, three units) of the welding boss620 are projectingly provided on the upper surface of the hub centralportion 621 at given intervals in the peripheral direction of the hub615.

In each of the tape reels 612 a, 612 b, the pivot 619 projectinglyprovided on the hub 615 of the lower flange 616 is fitted into the pivotholes 617 formed in the central portion 613 of the upper flange 614.Also, the welding bosses 620 projectingly provided on the hub 615 of thelower flange 616 are respectively fitted into their associated weldingboss holes 618 formed in the central portion 613 of the upper flange614. In the thus fitted state, in case where welding horns (not shown)are respectively contacted with the substantially central portions ofthe leading end faces (in FIGS. 2 and 4, the upper end faces) of thewelding bosses 620, the welding bosses 620 can be supersonically weldedrespectively. Due to this, the upper and lower flanges 614 and 616 canbe fixed with a given position relationship between them.

On the opposite surface 616 a (which is hereinafter referred to as abottom surface 616 a) of the lower flange 616 to the hub 615, there isdisposed a reference ring 624 which is used as a reference for workingthe tape reel using a metal mold. Also, in the portion of the bottomsurface 616 a of the lower flange 616 that exists inwardly of thereference ring 624 in the radial direction of the lower flange 616,there is formed a receiving surface 625 which can be used in thesupersonic welding of the welding boss 620. The receiving surface 625,when the welding boss 620 is welded supersonically, is contacted with awelding receiving base (not shown) to thereby allow the weldingreceiving base to receive pressures from the welding horns as well asvibrations caused by the oscillation of supersonic waves.

That is, referring to FIGS. 2 and 3, in the lower flange 616 of the Mcassette tape reel 612 a, the receiving surface 625 is composed of thelower surface (in FIG. 2) of a ring portion 626 which projects downwardin FIG. 2 annularly by a given amount from the bottom surface 616 aalong the base end of the hub central portion 621 of the bottom surface616 a of the lower flange 616. Also, the receiving surface 625 issituated slightly outwardly of just below the welding boss 620 in theradial direction of the lower flange 616. In a space formed between thereference ring 624 and receiving surface 625 of the bottom surface 616a, there is disposed a projecting portion 627 a such as a cavity number.

Also, referring to FIGS. 4 and 5, in the lower flange 616 of the Lcassette tape reel 612 b, the receiving surface is composed of two ormore (in FIG. 5, three) areas spaced at regular intervals in theperipheral direction of the lower flange 616 between the base end of thehub central portion 621 of the bottom surface 616 a of the lower flange616 and the inner peripheral surface of the reference ring 624. That is,in case where a space between the base end of the hub central portion621 of the bottom surface 616 a of the lower flange 616 and the innerperipheral surface of the reference ring 624 is divided into six equalareas in the area ratio, the receiving surface 625 is composed of thethree divided areas with one area between them, while the present threeareas project downward in FIG. 4 by a given amount over the remainingthree areas. The radial-direction inner ends of the respective areasforming the receiving surface 625 are situated almost directly below thewelding bosses 620 respectively. In the remaining areas 628 which do notform the receiving surface 625, there are disposed a projecting portion627 a for a cavity number, a projecting-out trace 627 b, and a gateprojecting portion 627 c, respectively.

Referring now to FIGS. 2 and 4, clearances C1, C2 along the verticaldirection in FIGS. 2 and 4 between the receiving surface 625 and thereference surface (in FIGS. 2 and 4, the lower surface) of the referencering 624 are substantially equal in the lower flange 616 of the Mcassette tape reel 612 a and in the lower flange 616 of the L cassettetape reel 612 b (C1=C2). Therefore, when the welding bosses 620 arewelded supersonically, the relative positions of the tape reels 612 a,612 b to the welding receiving base to be contacted by the receivingsurfaces 625 of the tape reels 612 a, 612 b need not be changed in the Mcassette tape reel 612 a and L cassette tape reel 612 b. Thanks to this,the supersonic welding of the welding bosses 620 of the M cassette tapereel 612 a and the supersonic welding of the welding bosses 620 of the Lcassette tape reel 612 b can be executed using the same equipment.

Next, description will be given below of the operation of the presentembodiment.

When the welding bosses 620 are welded supersonically, the receivingsurface 625 is contacted with the welding receiving base to therebyallow the welding base to receive pressures from the welding horns aswell as vibrations caused by the oscillation of the supersonic waves.The receiving surface 625 of the M cassette tape reel 612 a is composedof the lower surface (in FIG. 2) of the ring portion 626 which extendsannularly along the base end of the central portion 621 of the bottomsurface 616 a of the lower flange 616 and projects downward (in FIG. 2)by a given amount from the bottom surface 616 a. Also, the receivingsurface 625 of the L cassette tape reel 612 b is formed of three areaswhich are present between the base end of the central portion 621 of thebottom surface 616 a of the lower flange 616 and the inner peripheralsurface of the reference ring 624 and are spaced from each other atequal intervals in the peripheral direction of the lower flange 616.

Due to the above-mentioned position relationship between the receivingsurface 625 and reference ring 624, the receiving surface 625 contactedwith the welding receiving base supports the welding bosses 648substantially from directly below them. Therefore, the oscillationenergy of the supersonic waves from the welding horns can be transmittedeffectively from the welding horns to the welding bosses 620 withoutsuffering any loss due to the resonance of the portions of the tapereels 612 a, 612 b that are present between the welding bosses 620 andreference ring 624.

According to the above embodiment, the receiving surface 625 of the Mcassette tape reel 612 a is formed of the lower surface (in FIG. 2) ofthe ring portion 626 which extends annularly along the base end of thecentral portion 621 of the bottom surface 616 a of the lower flange 616and projects downward (in FIG. 2) by a given amount from the bottomsurface 616 a, and also the receiving surface 625 of the L cassette tapereel 612 b is formed of the three areas which are present between thebase end of the central portion 621 of the bottom surface 616 a of thelower flange 616 and the inner peripheral surface of the reference ring624 and are spaced from each other at equal intervals in the peripheraldirection of the lower flange 616. Therefore, the oscillation energy ofthe supersonic waves from the welding horns can be transmittedeffectively from the welding horns to the welding bosses 620 withoutsuffering any loss due to the resonance of the portions of the tapereels 612 a, 612 b that are present between the welding bosses 620 andreference ring 624. Thanks to this, not only the transmission efficiencyof the oscillation energy of the supersonic waves from the welding hornsto the welding bosses 620 can be enhanced, but also reduction in thewelding time as well as mass-production aptitude and welding stabilitycan be secured.

As described above, according to the first invention, since thereceiving surface, which is used when the welding bosses are weldedsupersonically, is formed in the opposite surface of the lower flange tothe hub, specifically, on the side of the present lower flange surfacethat is situated inside the reference ring in the radial direction ofthe lower flange, the transmission efficiency of the oscillation energyof the supersonic waves to the welding bosses 620 can be enhanced. Thismakes it possible not only to reduce the time necessary for supersonicwelding of the welding bosses but also to enhance the welding stability.

Also, since the distance between the reference ring and receivingsurface is set constant regardless of the sizes of the tape reels, thewelding operation can be enforced using the same equipment.

Next, description will be given below of an embodiment according asecond invention. Here, FIG. 6 is a half section view of the mainportions of a magnetic tape reel according to an embodiment of thesecond invention. By the way, the present embodiment is almost similarin structure to the conventional magnetic tape reel shown in FIGS. 20 to22 except for a few parts thereof. Therefore, the same parts thereof aregiven the same designations and thus the description thereof is omittedor simplified here.

The magnetic tape reel shown in FIG. 6 is an M-size magnetic tape reelto be provided in a digital video cassette (which is hereinafterreferred to as [DVC]) for use in a broadcasting station. On the innersurface of an upper flange 142, there is formed a sloping surface 142 bwhich slopes upward from the vicinity of a hub 145 outwardly in theradial direction of the upper flange 142; and, on the inner surface of alower flange 143, there is formed a sloping surface 143 b slopingdownward from the vicinity of the hub 145 outwardly in the radialdirection of the lower flange 143. By the way, in FIG. 6, to facilitatethe understanding of the sloping surfaces, the gradient thereof isexpressed exaggeratedly.

Also, on the inner surfaces of the upper and lower flanges 142, 143,adjacently to the side wall 145 b of the hub 145, there are formed flatsurfaces 142 c, 143 c intersecting at right angles to the side wall 145b and having a given width W between the side wall 145 b and slopingsurfaces 142 b, 143 b. The two flat surfaces 142 c, 143 c are formed ina ring shape which surrounds the side wall 145 b.

The widths W of the two flat surfaces 142 c, 143 c are set equal to eachother; and, this width W corresponds to or more than the tape windingthickness which is obtained before, after the winding of the magnetictape starts, the running speed and tape tension of the magnetic taperespectively become constant and the running of the magnetic tape isthereby stabilized. Also, a clearance H between the two flat surfaces142 c, 143 c is equal to the height of the side wall 145 b and isslightly larger than the width of the magnetic tape; and, the clearanceH is set as narrow as possible unless it provides an obstacle to therunning of the magnetic tape.

In the case of the present embodiment, since the magnetic tape reel isan M-size reel for use in a DVC, for the width 6.35 mm of the magnetictape, the widths W of the two flat surfaces 142 c, 143 c arerespectively 2.3 mm, and the clearance H between the two flat surfaces142 c, 143 c is 6.7 mm.

The upper and lower sloping surfaces 142 b, 143 b start to slope at theboundary portions c, d with respect to the two flat surfaces 142 c, 143c; and, as they approach outwardly in the radial direction, theclearance between the upper and lower flanges widens, thereby being ableto facilitate the running of the magnetic tape.

The magnetic tape is wound around the magnetic tape reel in such amanner that it is connected to one end of a leader tape and the otherend of the leader tape is fixed to the side wall 145 b of the hub 145 bya clamping pin.

Next, description will be given below of the operation of the presentembodiment.

In case where a magnetic tape cassette is loaded into a recording andreproducing apparatus and the winding operation of a magnetic tape isstarted, in the early winding stage, the rotating speed of the reeldrive means increases gradually and, therefore, the running speed of themagnetic tape also increases gradually. Due to this, in the earlywinding stage of the magnetic tape, the running condition of themagnetic tape is not stable but there is a fear that the magnetic tapecan be vibrated in the vertical direction.

However, in the early winding stage where the magnetic tape is woundbetween the two flat surfaces 142 c, 143 c, the upper and lower edges ofthe magnetic tape are regulated by the flat surfaces 142 c, 143 c of theupper and lower flanges and, therefore, even though the runningcondition of the magnetic tape is not stable, the magnetic tape isprevented from being vibrated in the vertical direction. As a result ofthis, the side edges of the magnetic tape are arranged in order, and thetape winding surface formed by the tape side edges becomes flat, therebybeing able to provide a good winding shape.

Also, when the magnetic tape is wound between the two sloping surfaces142 b, 143 b after it moves beyond between the two flat surfaces 142 c,143 c, not only the reel drive means has already been rotating at aconstant speed but also the tape speed and tape tension have also beenstabilized. Therefore, when the magnetic tape is wound between the twosloping surfaces 142 b, 143 b, there is no fear that the magnetic tapecan be vibrated in the vertical direction, thereby eliminating a fearthat the winding shape of the magnetic tape can be in disorder.Accordingly, a good winding shape of the magnetic tape can be obtainedover the entire areas on and between the upper and lower flanges 142,143.

Also, in case where the width W of the two flat surfaces 142 c, 143 c isin the range of 0.5-5.0 mm and the clearance H between the two flatsurfaces 142 c, 143 c is in the range of 6.6 m-6.8 mm, a good windingshape can be obtained.

By the way, the second invention is not limited to the above-mentionedembodiment but various changes and improvements are possible withoutdeparting from the subject matter of the second invention. For example,the second invention is not limited to the DVC but can also be appliedto any type of magnetic tape cassette.

As described above, according to the second invention, on the respectiveportions of the upper and lower flanges that are situated adjacently totheir associated hubs, there are formed the flat surfaces that intersectwith the side surfaces of the hubs at right angles and have a givenwidth in the radial direction of the respective flanges; and, therefore,during the initial winding time while the magnetic tape is wound betweenthe two flat surfaces of the upper and lower flanges, the side edges ofthe magnetic tape are defined by the two flat surfaces, therebyeliminating a fear that the magnetic tape can be vibrated in thevertical direction. Thanks to this, the winding surface of the magnetictape, which is formed by the side edges of the magnetic tape, can beformed as a flat surface, thereby being able to provide a good windingshape of the magnetic tape.

Next, description will be given below of an embodiment according to athird invention. Here, FIG. 7 is a plan view of a lower cassette half ofa magnetic tape cassette according to a first embodiment of the thirdinvention; and, FIG. 8 is a section view of the main portions of themagnetic tape cassette shown in FIG. 7.

In FIG. 7, a magnetic tape cassette 710 is structured such that a pairof tape reels 712 (in FIG. 7, a tape reel to be disposed on the rightside is not shown) with a magnetic tape t (see FIG. 20) are rotatablysupported on a lower cassette half 711 which makes a pair with an uppercassette half 710 a (see FIG. 8).

The lower cassette half 711 is integrally molded of synthetic resin suchas ABS resin and includes a pair of right and left (in FIG. 7) reelholes 711 a. Referring to use of the respective reel holes 711 a of thelower cassette half 711, in a state where the magnetic tape cassette 710is loaded into a drive apparatus (not shown), the tape reel driveportion (not shown) of the drive apparatus can be inserted into andremoved from the reel holes 711 a.

Referring to FIGS. 7 and 8, each of the tape reels 712 of the magnetictape cassette 710 comprises an upper flange 714, and a lower flange 716disposed opposed to the upper flange 714 and including a hub 715 on thesurface thereof opposed to the central portion 713 of the upper lange714.

The upper and lower flanges 714 and 716 are fixed in such a manner thatthe upper surface of the hub 715 of the lower flange 716 is contactedwith the lower surface of the central portion 713 of the upper flange714. The upper flange 714 is integrally molded of, for example,transparent synthetic resin, whereas the lower flange 716 is integrallymolded of, for example, opaque synthetic resin.

In the upper flange 714, there are formed a pivot hole 717 and a weldingboss hole 718. The pivot hole 717 is formed so as to penetrate throughthe substantially central position of the central portion 713 of theupper flange 714. In the case of the welding boss hole 718, at thepositions in the central portion 713 of the upper flange 714 thatcorrespond to welding bosses 720 (which will be discussed later), thesame number of welding boss holes 718 as the welding bosses 720 areformed so as to penetrate through the central portion 713 of the upperflange 714.

In the case of the lower flange 716, on the upper surface of the hub 715thereof, there are projectingly provided a pivot 719 and a welding boss720. Referring to the structure of the hub 715, on the periphery of thehub 715 that is distant in the radial direction from the hub centralportion 721, there is formed a side wall 722 serving as the windingsurface of the magnetic tape t, while the hub central portion 721 andside wall 722 are connected together by a plurality of ribs 723.

The pivot 719 is provided on and projected from the substantiallycentral position of the upper surface of the hub central portion 721.Also, in the case of the welding boss 720, two or more units of thewelding boss 720 are provided on and projected from the upper surface ofthe hub central portion 721 (in the present embodiment, one unit of thewelding boss 720 is projectingly provided every 120° in the peripheraldirection with the pivot 719 as the center thereof, that is, a total ofthree units of the welding boss 720 are provided).

In each of the tape reels 712, the pivot 719 projectingly provided onthe hub 715 of the lower flange 716 is fitted into the pivot hole 717formed in the flange portion 713 of the upper flange 714. Also, thewelding bosses 720 projectingly provided on the hub 715 of the lowerflange 716 are respectively fitted into their associated welding bossholes 718 formed in the central portion of the upper flange 714.

In the thus fitted state, in case where the welding horns (not shown)are respectively contacted with the substantially central portions ofthe leading end faces (in FIG. 8, the upper end faces) of the weldingbosses 720, the respective welding bosses 720 can be weldedsupersonically. Thanks to this, the upper and lower flanges 714 and 716can be fixed with a given position relationship between them.

On the bottom surface of the lower flange 716 that exists on theopposite side to the hub 715, not only there is disposed an outsideannular-shaped rib 724 but also, inwardly of the outside annular-shapedrib 724 in the radial direction of the lower flange 716, there isprovided an inside annular-shaped rib 725. The outside annular-shapedrib 724 and inside annular-shaped rib 725 are present at positions moredistant by a given amount in the radial direction from the pivot 719than the welding bosses 720:

The outside annular-shaped rib 724 has an outside diameter smaller by agiven amount than the inside diameter of the reel hole 711 a of thelower cassette half 711 and can be loosely fitted into the reel hole 711a.

Referring further to the lower flange 716, its large-thickness steppedportion 716 a formed to be continuous with the outside annular-shapedrib 724, which is disposed opposed to the edge portion of the reel hole711 a of the lower cassette half 711, has a thickness of a given valueor larger and thus, when compared with the remaining portions of thelower flange 716, the large-thickness stepped portion 716 a projectsslightly downward in FIG. 8.

The large-thickness stepped portion 716 a of the lower flange 716 notonly allows the lower flange 716 to have high rigidity but also, whenthe magnetic tape cassette 710 is not loaded into a drive apparatus (notshown), that is, when it is not in use, allows the tape reel 712 to besupported by the lower cassette half 711.

Now, description will be given below of the operation of the presentembodiment.

When the magnetic tape cassette 710 is not loaded into a drive apparatus(not shown), that is, when it is not in use, the large-thickness steppedportions 716 a of the lower flanges 716 of the tape reels 712 arerespectively contacted with the edge portions of the reel holes 711 aformed in the inner surface of the lower cassette half 711.

In this state, not only entry of dust into the interior of the magnetictape cassette 710 can be prevented but also the high dust-proof propertyof the magnetic tape cassette 710 can be secured.

Also, the tape reels 712 and the magnetic tape t wound around the tapereels 712 are supported through the large-thickness stepped portions 716a of the lower flanges 716 on the lower cassette half 711. Thanks to thesupport of the tape reels 712 on the lower cassette half 711 through thelarge-thickness stepped portions 716 a of the lower flanges 716 as wellas thanks to the high rigidity of the lower flanges 716 of the tapereels 712 due to provision of the large-thickness stepped portions 716a, even in the case of a tape reel having a large diameter size, therecan be prevented positively the deformation of the lower flanges 16 ofthe tape reels 712 due to the weight of the magnetic tape t when themagnetic tape cassette 710 is not in use. This makes it possible tosecure a sufficient clearance A between the lower flanges 716 and lowercassette half 711.

Next, description will be given below of an embodiment according to afourth invention. FIG. 9 is a section view of the main portions of amagnetic tape cassette according to an embodiment of the fourthinvention.

In a magnetic tape cassette 730 according to the present embodiment, onthe edge portions of reel holes 731 a formed in the inner surface (inFIG. 9, the upper surface) of a lower cassette half 731, there areprovided annular-shaped projecting portions 732 respectively. Theannular-shaped projecting portions 732, when the magnetic tape cassette730 is not in use, are respectively contacted with the outer surfaces ofthe lower flanges 741 of tape reels 740. Due to such contact, theannular-shaped projecting portions 732 not only can prevent dust fromentering the interior of the magnetic tape cassette 730 but also cansupport the weight of the tape reels 740 and the weight of a magnetictape t (see FIG. 20) wound around the tape reels 740.

Also, in the lower flanges 741 of the tape reels 740, thelarge-thickness portion 716 a (see FIG. 8) is not formed. On theradial-direction inside (in FIG. 9, the left side) portions of the edgeportions of the reel holes 731 a formed in the outer surfaces (in FIG.9, lower surfaces) of the lower flanges 741 of the tape reels 740, thereare provided annular-shaped ribs 742 respectively. The annular-shapedribs 742 respectively have an outside diameter smaller by a given amountthan the inside diameter of the reel holes 731 a of the lower cassettehalf 731 and thus can be loosely fitted into their associated reel holes731 a.

Further, on the radial-direction outside (in FIG. 9, the right side) ofthe annular-shaped ribs 742 provided on the lower flanges 741 of thetape reels 740, there are provided annular-shaped projections 743respectively. The annular-shaped projections 743, when the magnetic tapecassette 730 is not in use, are loosely fitted respectively with theirassociated annular-shaped recessed portions 733 formed in the innersurface of the lower cassette half 731 and are thus contacted with thelower cassette half 731. Due to this, the annular-shaped projections 743are able to support the weight of the tape reels 740 and also the weightof the magnetic tape t wound around the tape reels 740.

The remaining portions of the present embodiment are similar instructure to the previously-described embodiment of the third invention.

Now, description will be given below of the operation of the presentembodiment.

When the magnetic tape cassette 730 is not in use, not only theannular-shaped projecting portions 732 of the lower cassette half 731are respectively contacted with the mutually opposed outer surfaces ofthe lower flanges 741 of the tape reels 740 but also the annular-shapedprojections 743 of the lower flanges 741 are respectively fitted looselyinto their associated annular-shaped recessed portions 733 of the lowercassette half 731 and are thus contacted with the lower cassette half731.

In this state, entry of dust into the interior of the magnetic tapecassette 730 can be prevented as well as the high dust-proof property ofthe magnetic tape cassette 730 can be secured.

Also, the tape reels 740 and the magnetic tape t wound around the tapereels 740 are supported on the lower half cassette 731 through theannular-shaped projecting portions 732 of the lower cassette half 731and the annular-shaped projections 743 of the lower flanges 741. Thanksto the support of the tape reels 740 on the lower cassette half 731through the annular-shaped projecting portions 732 of the lower cassettehalf 731 and the annular-shaped projections 743 of the lower flanges741, even in the case of tape reels each having a large diameter size,the deformation of the lower flanges 741 of the tape reels 740 due tothe weight of the magnetic tape t can be prevented positively. Thismakes it possible to secure a sufficient clearance B between the lowerflanges 741 and lower cassette half 731.

As described above, according to the previously-described embodiment ofthe third invention, in the lower flanges 716 of the respective tapereels 740, there are formed the large-thickness stepped portions 716 awhich, when the magnetic tape cassette 710 is not in use, are contactedwith the edge portions of the reel holes 711 a formed in the innersurface of the lower cassette half 711. Therefore, entry of dust intothe interior of the magnetic tape cassette 710 can be prevented as wellas the high dust-proof property of the magnetic tape cassette 710 can besecured.

Also, thanks to the support of the tape reels 712 on the lower cassettehalf 711 through the large-thickness stepped portions 716 a of the lowerflanges 716 as well as thanks to the high rigidity of the lower flanges716 of the tape reels 712 due to provision of the large-thicknessstepped portions 716 a, even in the case of tape reels each having alarge diameter size, there can be prevented positively the deformationof the lower flanges 16 of the tape reels 712 due to the weight of themagnetic tape t when the magnetic tape cassette 710 is not in use. Thismakes it possible to secure a sufficient clearance A between the lowerflanges 716 and lower cassette half 711.

According to the above-mentioned embodiment of the fourth invention, inthe edge portions of the reel holes 731 a formed in the inner surfacesof the lower cassette half 731, there are respectively provided theannular-shaped projecting portions 732 which, when the magnetic tapecassette 730 is not in use, are contacted with the outer surfaces of thelower flanges 741 of the tape reels 740. Therefore, entry of dust intothe interior of the magnetic tape cassette 730 can be prevented as wellas the high dust-proof property of the magnetic tape cassette 730 can besecured.

Also, the annular-shaped projections 743, which can be loosely fittedinto their associated annular-shaped recessed portions 733 formed in theinner surface of the lower cassette half 731 when the magnetic tapecassette 730 is not in use, are respectively provided on theradial-direction outside of the annular-shaped ribs 742 disposed on thelower flanges 741 of the tape reels 740.

Therefore, when the magnetic tape cassette 730 is not in use, the weightof the tape reels 740 and the weight of the magnetic tape t wound aroundthe tape reels 740 can be supported by the lower cassette half 731through the annular-shaped projecting portions 732 of the lower cassettehalf 731 and the annular-shaped projections 743 of the lower flanges741. Thanks to this, even in the case of tape reels each having a largediameter size, the deformation of the lower flanges 741 of the tapereels 740 due to the weight of the magnetic tape t when the magnetictape cassette 730 is not in use can be prevented positively, therebybeing able to secure a sufficient clearance B between the lower flanges741 and lower cassette half 731.

As described above, according to the third invention, the lower flangeof each tape reel has a large-thickness stepped portion is formed to becontinuous with an outside annular-shaped rib, while the large-thicknessstepped portion includes a portion which is disposed opposed to the edgeportion of its associated reel hole of the lower cassette half and thethickness of which is set at a given value or larger.

Therefore, not only, when the magnetic tape cassette 730 is not in use,high dust-proof property can be secured in the interior of the magnetictape cassette 730, but also the deformation of the lower flanges of thetape reels can be prevented positively to thereby be able to secure asufficient clearance between the lower flanges and lower cassette half.

Also, according to the fourth invention, on the edge portions of thereel holes formed in the inner surface of the lower cassette half, thereare disposed not only the annular-shaped projecting portions but alsothe annular-shaped recessed portions on the radial-direction outside ofthe annular-shaped projection portions, and, at the positions in theinner surfaces of the lower flanges of the tape reels that are opposedto the annular-shaped recessed portions, there are disposed theannular-shaped projections which can be loosely fitted into theannular-shaped recessed portions.

Therefore, not only, when the magnetic tape cassette is not in use, highdust-proof property can be secured in the interior of the magnetic tapecassette, but also the deformation of the lower flanges of the tapereels can be prevented positively to thereby be able to secure asufficient clearance between the lower flanges and lower cassette half.

Next, description will be given below of an embodiment according to afifth invention. Here, FIG. 10 is a plan view of a lower flange of atape reel of a magnetic tape cassette according to an embodiment of thefifth invention; FIG. 11 is a section view of the lower flange shown inFIG. 10, taken along the arrow line A—A in FIG. 10; and, FIG. 12 is anenlarged section view of the B portion of the lower flange shown in FIG.11.

Firstly, the whole structure of a magnetic tape cassette according tothe present embodiment will be described below with reference to FIG.24. The present magnetic tape cassette is structured such that a pair oftape reels 810 around which a magnetic tape t can be wound are rotatablysupported on a lower cassette half 812 making a pair with an uppercassette half 811.

Referring now to FIGS. 10 and 11, each tape reel 810 comprises an upperflange 814 (see FIG. 24) including a central portion 813 (see FIG. 24),and a lower flange 816 disposed opposed to the upper flange 814 andincluding a hub 815 provided on the surface thereof opposed to the upperflange 814. The upper flange 814 and lower flange 816 are fixed with agiven clearance between them. The upper flange 814 is integrally moldedof, for example, transparent synthetic resin, whereas the lower flange816 is integrally molded of, for example, opaque synthetic resin.

In the upper flange 814, there are formed a pivot hole 817 (see FIG. 24)and welding boss holes 818 (see FIG. 24). The pivot hole 817 is formedsubstantially centrally in the central portion 813 of the upper flange814 so as to penetrate through the upper flange 814. The welding bossholes 818 are formed at the positions in the central portion 813 of theupper flange 814 that respectively correspond to their associatedwelding bosses 820 (which will be discussed later), while the number ofthe welding boss holes 818 is set equal to that of the welding bosses820.

In the case of the lower flange 816, a pivot 819 and welding bosses 820are respectively provided on and projected from the upper surface of thehub 815. That is, the hub 815 is structured such that, in the peripheryof the hub 815 distant radially from the central portion 821 of the hub815, there is formed an inner side wall 822; and also, in the portion ofthe periphery of the hub 815 that is further distant radially than theinner side wall 822, there is formed an outer side wall 823 serving as awinding surface for a magnetic tape t (see FIG. 24). The inner and outerside walls 822 and 823 are connected together by a plurality of ribs 824which are disposed along the radial direction of the hub 815.

The pivot 819 is provided on and projected from the substantiallycentral position of the upper surface of the hub central portion 821. Inthe case of the welding bosses 820, at the positions of the uppersurface of the inner side wall 822 that are distant in the radialdirection of the hub 815 from the pivot 819, there are two or more unitsof the welding bosses 820 such that they are spaced from each other atgiven intervals in the peripheral direction of the inner side wall 822.The ribs 824 are respectively interposed between the side surface of theinner side wall 822 and the inner surface of the outer side wall 823that is disposed opposite thereto in the radial direction of the hub815.

In each tape reel 810, the pivot 819 projectingly provided on the hub815 of the lower flange 816 is fitted into the pivot hole 817 formed inthe central portion of the upper flange 814. Also, the welding bosses820 projectingly provided on the hub 815 of the lower flange 815 arerespectively fitted into their associated welding boss holes 818 formedin the central portion 813 of the upper flange 814.

In this state, in case where welding horns (not shown) are contactedwith the substantially central portions of the leading end face (in FIG.11, the substantially central portions of the upper end face) of therespective welding bosses 820, the welding bosses 820 can be weldedsupersonically. Thanks to this, the upper and lower flanges 814 and 816can be fixed with a given position relationship between them.

Referring now to FIGS. 10-12, in the surface 816 a (in FIG. 11, theupper surface) of the lower flange 816 that is opposed to the upperflange 814, there can be formed a plurality of air discharging recessedportions 825 at given intervals in the peripheral direction of the lowerflange 816 when the lower flange 816 is worked or molded using a metalmold. The air discharging recessed portions 825, when they are viewedfrom the top surfaces thereof, are respectively formed in asubstantially fan-like shape fanning out outwardly in the radialdirection of the lower flange 816, while they respectively have a depthof, for example, 0.2 mm. The air discharging recessed portions 825 arerespectively used to discharge the air that enters together with themagnetic tape t as the magnetic tape t is wound around the tape reels.

In the respective edge portions 825 a of the air discharging recessedportions 825, there are formed sloping surfaces 825 c which are used toconnect the bottom surfaces 825 b of the air discharging recessedportions 825 with the upper surface (in FIG. 11) of the lower flange816. On the boundary portions between the bottom surfaces 825 b andsloping surfaces 825 c of the air discharging recessed portions 825 aswell as on the boundary portions between the upper surface (in FIG. 11)of the lower flange 816 and the sloping surfaces 825 c of the airdischarging recessed portions 825, there are applied required curvedshapes 826 over the entire peripheries of the air discharging recessedportions 825, respectively, so that no edge can be produced in the aboveboundary portions. By the way, not only in the magnetic tape cassettefor a beta cam to be described in the present embodiment, but also inany other magnetic tape cassette, the R (curved) shape 826 maypreferably have a diameter in the range of 1 mm to 4 mm (R1 to R4).

By the way, the air discharging recessed portions 825 may berespectively formed as air discharging penetration holes (not shown)which penetrate through the lower flange 816. Also, although therequired curved shapes 826 may be preferably applied over the entireperipheries of the air discharging recessed portions 825, since it isbelieved that the magnetic tape t can be damaged extremely often by theedge portions of at least two sides (the boundary portions between theupper surface 816 a of the lower flange 816 and the sloping surfaces 825c) of the air discharging recessed portions 825 in the flange radialdirection, the curved shapes 826 maybe applied to at least such twosides of the respective air discharging recessed portions 825.

Now, description will be given below of the operation of the presentembodiment.

When the magnetic tape t is taken up around the tape reels of themagnetic tape cassette, the air discharging recessed portions 825 of thelower flange 816 function as flow passages which discharge theaccompanying air externally of the tape reels, thereby being able toprevent the magnetic tape t from being wound in disorder. In this case,even in case where the magnetic tape t is contacted with the edgeportions 825 a of the air discharging recessed portions 825 of the lowerflange 816, the required curve shapes 826 applied to the edge portions825 a can eliminate the fear that the magnetic tape t can be damaged bythe edge portions 825 a.

As described above, according to the present embodiment, on the boundaryportions between the bottom surfaces 825 b and sloping surfaces 825 c ofthe air discharging recessed portions 825 of the lower flange 816 aswell as on the boundary portions between the upper surface 816 a (inFIG. 11) of the lower flange 816 and the sloping surfaces 825 c of theair discharging recessed portions 825, there are applied the requiredcurve shapes 826, respectively. Due to this, the damage of the magnetictape t otherwise possibly caused by its contact with the lower flanges816 of the tape reels can be prevented. Thanks to this, the presentembodiment is able to cope with the enhanced density of the magnetictape recording.

As described above, according to the fifth invention, on the edgeportions of at least two flange-radial-direction sides of the airdischarging recessed portions or air discharging penetration holesformed in the upper or lower flange, there are applied the requiredcurve shapes respectively.

Therefore, the damage of the magnetic tape due to its contact with thetape reels can be prevented. Due to this, the fifth invention is able tocope with the enhanced density of the magnetic tape recording.

Next, description will be given below in detail of an embodimentaccording to sixth and seventh inventions. FIG. 13 is an exploded planview of a hub and a clamp member included in a magnetic tape reel of abeta cam L cassette according to an embodiment of the fifth invention.And, FIG. 14(a) is a plan view of the hub and clamp member included inthe magnetic tape reel according to the embodiment of the fifthinvention, showing their combined state, and FIG. 14(b) is a side viewthereof. By the way, the magnetic tape reel includes two flanges on theupper and lower portions of the hub but, in FIGS. 13 and 14, theillustration of these flanges is omitted.

On the central portion of the upper surface of the hub 902, there isdisposed a rib 904 which can be pressed by a reel holder within the betacam L cassette; and, in the radial direction of the upper surface of thehub 902, there are disposed a plurality of welding ribs 906 which can besupersonically welded to the upper flange. Also, in the peripheralsurface of the hub 902, there is formed a recessed portion 912 which isused to hold and fix the other end of a leader tape 912, with one endthereof connected to the magnetic tape, using a clamp member 908. Incase where the clamp member 908 is fitted into the recessed portion 910,the clamp member 908 holds and fixes the leader tape 912.

Referring to the structure of the hub 902, the peripheral surface 902 aof the left (in FIG. 13) half section thereof is formed as a slopingsurface which increases in diameter as it goes downward and approachesthe portion (in FIG. 13, the left end portion) thereof opposed to therecessed portion 910. Also, the peripheral surface of the right (in FIG.13) half section of the hub 902 is formed as a half-cylindrical shape,and the present peripheral surface does not slope but is parallel to theaxial direction B of the hub 902. A difference d between the lowerportion of the sloping surface and the upper portion of the slopingportion, preferably, may be in the range of 0.1-0.5 mm. In the case ofthe present embodiment, the difference d between the lower portion ofthe sloping surface and the upper portion of the sloping portion is setat 0.4 mm. By the way, the height H of the hub 902 is set at 13.5 mm,while the diameter D of the hub excluding the sloping surface is set at36 mm.

On the other hand, the peripheral surface 908 a of the clamp member 908is formed as a sloping surface which increases in diameter as it goestoward the upper portion thereof and, when it is viewed from the topsurface thereof, approaches the center (in FIG. 14(a), the right end) ofthe recessed portion 910. The inner surface of the clamp member 908 isformed so as to be parallel to the axial direction B of the hub 902.And, as shown in FIG. 14(b), the sloping peripheral surface 902 a of thehub 902 and the sloping peripheral surface 908 a of the clamp member 908are parallel to each other when they are viewed from the side surfacesthereof.

According to the present structure, similarly to the tape reel disclosedin the previously cited Japanese Utility Model Unexamined PublicationNo. Sho.58-187083, since a magnetic tape to be wound around the hub 902is contacted with either the upper flange or lower flange every 180°when it is viewed from the top surface thereof so that the movementthereof in the vertical direction is restricted, there is no possibilitythat the magnetic tape wound around the hub 902 can project in part inthe axial direction B of the hub 902.

According to the present embodiment, since the hub 902 is structuredsuch that only the peripheral surface 902 a of the left half sectionthereof slopes, after molded, the hub 902 can be pulled out as it is inthe axial direction B; that is, the hub 902 can be molded withoutcomplicating a metal mold. Also, similarly, since the clamp member 908is structured such that only the peripheral surface 908 a slopes, theclamp member 908 can be molded without complicating a metal mold.

By the way, in the present embodiment, the entire area of the peripheralsurface 902 a of the left (in FIG. 14) half section of the hub 902 isformed as a sloping surface increasing in diameter toward the portionthat is opposed 180° to the recessed portion; however, as shown in FIG.15, only the neighboring portion 902 b of the portion opposed 180° tothe recessed portion maybe formed as a sloping surface which increasesin diameter as it goes toward the lower portion thereof and also as itgoes further in the radial direction.

Referring further to the hub 902 shown in FIG. 15, the portion 902 bopposed 180° to the recessed portion is structured such that, when it isviewed from the top surface thereof, the peripheral surface thereofincreases in diameter substantially in the same manner as the clampmember 908. When it is viewed from the side surface thereof, theperipheral surface of the portion 902 b is formed such that theperipheral surface thereof increases in diameter as it goes toward thelower portion thereof. The increased-diameter portion 902 b may bemolded integrally with the hub 902, or may be molded separately from thehub 902. In both cases, the increased-diameter portion 902 b is easy tomold.

As described above, according to the sixth and seventh inventions, sincethe hub includes the sloping portion only one side in the axialdirection thereof and the opposite side portion of the sloping portion,that is, the recessed portion to be fitted by the clamp member does notslope, after molded, the hub can be pulled out as it is along the axialdirection thereof. This eliminates the use of a complicated metal moldusing a sliding core and the hub can be manufactured easily using ametal mold having a simple structure. Further, since the hub includes asloping surface in the 180° opposed portion, when the magnetic tape iswound, the magnetic tape can be prevented against movement in thevertical direction, which makes it possible for the magnetic tape toprovide a good winding shape.

Next, description will be given below of an embodiment according to aneighth invention. FIG. 16 is a schematic plan view of a magnetic tapetake-up apparatus according to an embodiment of the eighth invention.

Referring now to FIG. 16, in the present magnetic tape take-up apparatus1010, a magnetic tape (not shown), which is being wound by a reel drivemechanism (not shown) from a tape supply source (not shown) onto thetape reel 1013 of a magnetic tape cassette 1011 with its cassette half1012 held by a half hold mechanism 1020, is energized near to the upperflange 1014 (in FIG. 16, the upper side) of the tape reel 1013 in anon-contact manner by a magnetic field generating mechanism 1030 tothereby arrange the winding shape of the magnetic tape with the innersurface of the upper flange 1014 of the tape reel 1013 as a reference.

Conventionally, the tape reel 1013 of the magnetic tape cassette 1011 isformed of ABS resin; but, on the other hand, according to the presentembodiment, in order to reduce the rate of occurrence of heat loss asmuch as possible, the tape reel 1013 is formed of polystyrene.

With the lower surface of the cassette half 1012 of the magnetic tapecassette 1011 engaged with a support plate 1021, the half hold mechanism1020 brings a pair of half buckets 1022 into engagement with the edgeportion of the upper surface of the cassette half 1012 to thereby holdthe cassette half 1012 in a given position. The half buckets 1022 aresupported on a winder panel 1023 in such a manner that they can be movedin the vertical direction in FIG. 16; and, specifically, they can bemoved in the vertical direction in FIG. 16 by their associated bucketoperating air cylinders 1024.

The reel drive mechanism is structured such that, for example, therotary shaft of an electric motor (not shown) is fitted into the tapereel 1013 of the magnetic tape cassette 1011 and, by rotating theelectric motor forwardly or reversely, the tape reel 1013 can be rotatedin a given rotation direction. That is, in this manner, the reel drivemechanism winds the magnetic tape from the tape supply source around thetape winding surface 1015 of the tape reel 1013 at a winding speed of 2m/s and with a winding tension of 65 g.

The magnetic field generating mechanism 1030 is structured such that amagnet is fixed to the inner surface (in FIG. 16, the lower surface) ofa magnet mounting panel 1032, and the mechanism 1030 is disposed opposedto the upper surface of the cassette half 1012 of the magnetic tapecassette 1011.

The magnet 1031 is a magnet formed substantially in a circular shape.And, substantially in the central portion of the magnet 1031, there isopened up a penetration hole 1033, so that the magnet 1031 is formed asa doughnut-shaped magnet. Also, the magnet 1031 is formed of neodymiumand has a thickness of 16 mm and a magnetic flux density of 12800-13300G. A yoke 1034 (a shield plate) having a thickness of 13 mm is appliedto the back surface of the magnet 1031.

The area of the portion (the area of the lower surface in FIG. 16) ofthe magnet 1031 that is opposed to the upper surface of the cassettehalf 1012 of the magnetic tape cassette 1011 is set 1.3 times the areaof the side surface side of the magnetic tape to be wound around thetape winding surface 1015 of the tape reel 1013. Due to this, a magneticfield given by the magnet 1031 can be applied uniformly onto the sidesurface of the magnetic tape from the upper flange 1014 side of the tapereel 1013. In case where the present area is less than 1.3 times, amagnetic field acting on the winding end portion of the magnetic tapebecomes weak, thereby causing the winding end portion of the magnetictape to be arranged in disorder.

The magnetic field generating mechanism 1030, with the movement of themagnet mounting panel 1032 in the downward direction in FIG. 16,energizes the tape reel 1013 downward in FIG. 16 using a reel holdmember 1035 which is projected out from the penetration hole 1033 of themagnet 1031. And, the magnetic field generating mechanism 1030 stops themovement of the magnet mounting panel 1032 at a position (which ishereinafter referred to as a tape winding position) where a clearance Lbetween the lower surface (in FIG. 16) of the magnet 1031 and the uppersurface of the cassette half 1012 of the magnetic tape cassette 1011 is10 mm, and allows the magnet 1031 to apply its magnetic field from theupper flange 1014 side (in FIG. 16, the upper side) of the tape reel1013 onto the side surface side (in FIG. 16, the upper side) of themagnetic tape. By the way, a clearance between the upper surface of thecassette half 1012 and the upper surface of the upper flange 1014 of thetape reel 1013 is 4 mm and, therefore, a clearance between the lowersurface of the magnet 1031 and the upper surface of the upper flange1014 is 14 mm.

The magnet mounting panel 1032 is supported so as to be movable to twosides: that is, one side (in FIG. 16, lower side) where a clearancebetween the winder panel 1023 and itself is narrowed; and the other side(in FIG. 16, upper side) where the clearance is widened. And, the magnetmounting panel 1032 can be moved by panel operating air cylinders 1036.

Specifically, the magnet mounting panel 1032, when the cassette half1012 of the magnetic tape cassette 1011 is loaded, is moved by the paneloperating air cylinders 1036 to the side (in FIG. 16, upper side) wherethe clearance between the winder panel 1023 and itself is widened (aposition shown in FIG. 16; which is hereinafter referred to as acassette half loading position). This makes it possible to facilitatethe loading of the cassette half 1012.

Also, the magnet mounting panel 1032, when the magnetic tape is woundaround the tape reel 1013, is moved by the panel operating air cylinders1036 to the side (in FIG. 16, lower side), where the clearance betweenthe winder panel 1023 and itself is narrowed, up to the tape windingposition. Due to this, at the tape winding position, the tape reel 1013can be energized to the lower side in FIG. 16 through the reel holdmember 1035.

Now, description will be given below of the operation of the presentembodiment.

When the magnetic tape is wound around the tape reel 1013 of themagnetic tape cassette 1011, firstly, with the magnet mounting panel1032 set at the cassette half loading position, the cassette half 1012of the magnetic tape cassette 1011 is inserted into between the halfbuckets 1022 and support plate 1021.

Next, by actuating the bucket operating air cylinders 1024, the cassettehalf 1012 of the magnetic tape cassette 1011 is held in a given positionbetween the half buckets 1022 and support plate 1021. At the same time,by actuating the panel operating air cylinders 1036, the magnet mountingpanel 1032 is moved to thereby set the magnet 1031 at the tape windingposition.

At the then time, the clearance L between the lower surface (in FIG. 16)of the magnet 1031 and the upper surface of the cassette half 1012 ofthe magnetic tape cassette 1011 is maintained at 10 mm (the clearancebetween the magnet 1031 and upper flange 1014 is maintained at 14 mm),and the magnet 1031 applies a magnetic field onto the magnetic tapebeing wound from the upper flange 1014 side (in FIG. 16, from the upperside) of the tape reel 1013.

In this state, in case where the electric motor of the reel drivemechanism is rotated, the tape reel 1013 is rotated in a given rotationdirection and the magnetic tape from the tape supply source is woundaround the tape winding surface 1015 of the tape reel 1013 at thewinding speed of 2 m/s and with the winding tension of 65 g.

Therefore, the winding shape of the magnetic tape can be arranged withthe inner surface of the upper flange 1014 of the tape reel 1013 of themagnetic tape cassette 1011 as a reference.

Next, the present inventors have checked the influence of the clearanceL between the magnet 1031 and the upper surface of the cassette half1012 of the magnetic tape cassette 1011 on the winding shape of themagnetic tape wound around the tape reel 1013 of the magnetic tapecassette 1011.

In case where the above clearance L was set at less than 8 mm, forexample, L=5 mm (the clearance between the magnet 1031 and upper flange1014 was 9 mm), the action of the magnetic field given by the magnet1031 was excessively strong so that, when the magnetic tape was wound,the upper flange 1014 of the tape reel 1013 was contacted with the innersurface of the cassette half 1012 to thereby cause friction betweenthem.

On the other hand, in case where the clearance L exceeds 13 mm, forexample, the clearance L=15 mm (the clearance between the magnet 1031and upper flange 1014 was 19 mm), the action of the magnetic field givenby the magnet 1031 was excessively weak so that the winding shape of theentire magnetic tape was found poor.

However, as in the present embodiment, in the case of the clearance L=10mm (the clearance between the magnet 1031 and upper flange 1014 was 14mm), the friction, which could otherwise be caused between the upperflange 1014 of the tape reel 1013 and the inner surface of the cassettehalf 1012 due to their mutual contact in the magnetic tape windingoperation, could be prevented positively. Also, the rate of occurrenceof the poor magnetic tape winding shape could be reduced by theoptimization of the clearance L and proper selection of the magnetictape.

Also, the inventors have checked the influences of the magnetic tapewinding speed by the reel drive mechanism on the tape reel 1013 with thewinding tension set at 65 g. The check results are shown in FIG. 17.

As can be seen from FIG. 17, in case where the winding speed is set at 2m/s as in the present embodiment, the temperature of the pivot portion(the projecting portion of the tape winding surface 1015) of the tapereel 1013 can be controlled down to a low level (in FIG. 17, approx. 36°C.), thereby eliminating a fear that a heat loss can be incurred in thepivot portion.

On the other hand, in case where the winding speed is equal to or higherthan 3 m/s, the temperature of the pivot portion of the tape reel 1013rises suddenly (in FIG. 17, approx. 40-70° C.); specifically, in casewhere the temperature of the pivot portion is 40° C. or higher, a heatloss can be incurred in the pivot portion.

Further, the inventors have checked the influences of the magnetic tapewinding speed by the reel drive mechanism on the magnetic tape windingshape with the winding tension set at 65 g. The check results are shownin FIG. 18.

As can be seen from FIG. 18, in case where the winding speed is 2 m/s asin the present embodiment, the rate of occurrence of the poor magnetictape winding shape can be controlled down to a low level (in FIG. 18,30-odd %).

On the other hand, in case where the winding speed is equal to or higherthan 3 m/s, the rate of occurrence of the poor magnetic tape windingshape rises suddenly (in FIG. 18, 60-odd %-100%).

Further, the present inventors have checked the influences of thewinding tension of the magnetic tape by the reel drive mechanism on themagnetic tape winding shape with the winding speed set at 2 m/s. Thecheck results are shown in FIG. 19. By the way, these data are obtainedthrough proper selection of the magnetic tape.

As can be seen from FIG. 19, in case where the winding tension is 65 gas in the present embodiment, the rate of occurrence of the poormagnetic tape winding shape is 0%.

On the other hand, in case the winding tension exceeds 65 g, the rate ofoccurrence of the poor magnetic tape winding shape rises suddenly (inFIG. 19, 60-odd %).

In case where the winding tension is less than 65 g, it is difficult tosecure the winding hardness of the magnetic tape.

As described above, according to the present embodiment, using the reeldrive mechanism, the magnetic tape from the tape supply source is takenup around the tape winding surface 1015 of the tape reel 1013 of themagnetic tape cassette 1011 at the winding speed of 2 m/s and with thewinding tension of 65 g. Also, to the magnetic tape being wound aroundthe tape reel 1013 by the reel drive mechanism, there is applied amagnetic field by the magnet 1031 formed of neodymium and having amagnetic flux density of 12800-13300 G from a position which is presenton the upper flange 1014 side (in FIG. 16, the upper side) of the tapereel 1013 and has the clearance L=10 mm with respect to the cassettehalf 1012 (the clearance between the magnet 1031 and upper flange 1014is 14 mm).

Thanks to this, the winding shape of the magnetic tape can be arrangedwith the inner surface of the upper flange 1014 of the tape reel 1013 asa reference, the running state of the magnetic tape in the recording andreproducing apparatus can be stabilized, and the running passage of themagnetic tape can be positively prevented from being shifted greatly.

For example, in the recording and reproducing apparatus 460 as shown inFIG. 28, the magnetic tape 462 wound around the tape reel 461 by themagnetic tape take-up apparatus according to the present embodiment isable to run along the running passage shown by a solid line in FIG. 28without shifting from the running passage.

In other words, the magnetic tape 462 played out from the tape reel 461is lifted once up to the upper limit position by the tape guide TG1through the tape guide TG0, the magnetic tape 462 at the upper limitposition is controlled in position by the tape guide TG1, after then,the magnetic tape 462 is controlled in position to its original ornormal position between the tape guides TG2 and TG3 by the tape guideTG2, and the magnetic tape 462 is contacted with the recording andreproducing head 464 at a given relative position.

This makes it possible to positively prevent occurrence of unrepairableserious defects in the recording and reproduction of the magnetic tape462 such as reduced output and poor interchangiability.

As described above, according to the eighth invention, in case where thetape reel is rotated by the drive means, the magnetic tape is woundaround the tape reel at the winding speed of 2-2.5 m/s and with thewinding tension of 60-70 g; and, the magnetic field generating meansincluding a magnet formed of neodymium and having a magnetic fluxdensity of 12800-13300 G applies a magnetic field to the magnetic tapefrom a position opposed to the upper flange of the tape reel with aclearance of 12-17 mm between them. Therefore, the winding shape of themagnetic tape can be arranged with the upper flange of the tape reel asa reference, which makes it possible to stabilize the running of themagnetic tape in the recording and reproducing apparatus.

Also, since the area of the portion of the magnetic field generatingmeans that is opposed to the upper flange of the tape reel is set 1.3times or more the area of the side surface side of the magnetic tape tobe wound around the tape reel, the magnetic field given by the magneticfield generating means can be applied evenly to the magnetic tape fromthe upper flange side of the tape reel, thereby being able to positivelyprevent the magnetic tape from being wound in disorder.

Although description has been given heretofore of the preferredembodiments of the invention, the present invention is not limited tothese embodiments but other various changes and modifications are alsopossible. For example, the structures of the respective illustratedembodiments may be properly combined together. Also, the invention canalso apply to other magnetic tape cassettes than DVC and beta cam.

INDUSTRIAL APPLICABILITY OF THE INVENTION

According to the first invention, since the receiving surface for use inthe supersonic welding of the welding bosses is formed in the portion ofthe opposite surface of the lower flange of the tape reel to the hubthat is situated inside the reference ring in the radial direction, theefficiency of transmission of the oscillation energy of the supersonicwaves to the welding bosses can be enhanced. This not only can reducethe time necessary for the supersonic welding of the welding bosses butalso can enhance the welding stability.

Also, because the distance between the reference ring and receivingsurface is set constant regardless of the sizes of the tape reels, thewelding can be enforced using the same equipment.

According to the second invention, since, in the portions of the upperand lower flanges that adjoin the hub, there are formed flat surfacesextending at right angles to the side surface of the hub and having agiven width in the radial direction of the flanges, during the initialwinding stage while the magnetic tape is being wound between the flatsurfaces of the upper and lower flanges, the side edges of the magnetictape are formed by the flat surfaces, thereby eliminating a fear thatthe magnetic tape can be vibrated in the vertical direction. Therefore,the winding surface to be formed by the side edges of the magnetic tapebecomes flat and thus a good winding shape can be obtained in themagnetic tape wound.

According to the third invention, the lower flange of the tape reelincludes a large-thickness stepped portion which is formed to becontinuous with the outside annular-shaped rib, while the thickness ofthe portion of the large-thickness stepped portion opposed to the edgeportion of the reel hole of the lower cassette half is set at a givenvalue or more.

Therefore, high dust-proof property can be secured in the interior ofthe tape reel when the magnetic tape cassette is not in use, thedeformation of the lower flange of the tape reel can be preventedpositively, and a sufficient clearance between the lower flange andlower cassette half can be secured.

According to the fourth invention, in the edge portion of the reel holeformed in the lower cassette half, there are disposed not only theannular-shaped projecting portion but also, outside the annular-shapedprojecting portion in the radial direction, the annular-shaped recessedportion; and, at the position in the inner surface of the lower flangeof the tape reel that is opposed to the annular-shaped recessed portion,there is disposed the annular-shaped projection 5 which can be looselyfitted into the annular-shaped recessed portion.

Thanks to this, high dust-proof property can be secured in the interiorof the tape reel when the magnetic tape cassette is not in use, thedeformation of the lower flange of the tape reel can be preventedpositively, and a sufficient clearance between the lower flange andlower cassette half can be secured.

According to the fifth invention, the required R shapes are respectivelyapplied to the edge portions of at least flange-radial-direction twosides of the air discharging recessed portions or air dischargingpenetration holes formed in the upper or lower flange.

Thanks to this, the damage of the magnetic tape due to its contact withthe edge portions of the air discharging recessed portions or airdischarging penetration holes of the upper or lower flange of the tapereel can be prevented, which allows the tape reel to cope with theenhanced density of the magnetic tape recording.

According to the sixth and seventh inventions, since the hub isstructured such that only one side in the axial direction thereof slopesand the opposite side of the sloping portion, that is, the recessedportion to be fitted with the clamp member does not slope, after molded,the hub as it is can be pulled out along the axial direction thereof.This eliminates the provision of a complicated metal mold using a slidecore and thus the hub can be manufactured easily using a metal moldhaving a simple structure. Further, because the hub includes the slopingsurface in the 180° opposed portion, the magnetic tape can be preventedfrom being moved in the vertical direction when it is wound, therebybeing able to obtain a good winding shape of the magnetic tape.

According to the eighth invention, in case where the drive means rotatesthe tape reel, not only the magnetic tape is wound around the tape reelat the winding speed of 2-2.5 m/s and with the winding tension of 60-70g, but also the magnetic field generating means including a magnetformed of neodymium and having a magnetic flux density of 12800-13300 Gapplies a magnetic field to the magnetic tape from a position opposed tothe upper flange of the tape reel with a clearance of 12-14 mm betweenthem. Thanks to this, the winding shape of the magnetic tape can bearranged with the upper flange of the tape reel as a reference, therebybeing able to stabilize the running of the magnetic tape in therecording and reproducing apparatus.

Also, since the area of the portion of the magnetic field generatingmeans opposed to the upper flange of the tape reel is set 1.3 or moretimes the area of the side surface side of the magnetic tape to be woundaround the tape reel, the magnetic field given by the magnetic fieldgenerating means can be applied uniformly to the magnetic tape from theupper flange side of the tape reel, which makes it possible topositively prevent the magnetic tape from being wound in disorder.

What is claimed is:
 1. A magnetic tape reel, comprising: a hub forwinding a magnetic tape therearound; and a clamp member; wherein theouter surface of said clamp member for holding a leader tape betweenitself and a recessed portion formed in said hub and a peripheralsurface of said hub that, when viewed from the top plan surface of saidhub, is disposed 180° opposed to said recessed portion are respectivelytapered surfaces which slope in mutually opposite directions withrespect to the axis of rotation of said magnetic tape reel.
 2. Themagnetic tape reel of claim 1, wherein the outer surface of said clampmember decreases in diameter from an upper portion to a lower portion ofthe clamp member.
 3. The magnetic tape reel of claim 2, wherein therecessed portion of the hub is not sloped.
 4. A method for manufacturinga magnetic tape reel having a structure that, in a hub for winding amagnetic tape therearound, there is formed a recessed portion forholding a leader tape using a clamp member and the peripheral surface ofsaid hub that, when viewed from the top plan surface of said hub, isdisposed 180° opposed to said recessed portion is a tapered surfacesloping toward the axis of rotation of said hub, said method comprisingthe steps of: injection molding said magnetic tape reel; and, pullingout said injection molded magnetic tape reel along the axial directionthereof.
 5. The method for manufacturing a magnetic tape reel of claim4, wherein the recessed portion of the hub is not sloped.